In this revised application, we seek competitive renewal of our program project, The Role of Human Milk in Infant Nutrition and Health, which is now entering its 31st year. This is a unique research program on human milk bioactive factors that addresses a long-standing priority of NICHD. Our program project involves a highly interactive, interdisciplinary team of senior and junior investigators with cores and projects at Cincinnati, Mexico, and Boston. Breastfeeding conveys potent bioactive factors that protect child health. During the current grant cycle we have shown that the human milk glycans, particularly, the a1,2 fucosyl (secretor) oligosaccharides and their high molecular weight glycoconjugates, are a major new class of antimicrobial agents. We have achieved initial synthesis of human milk secretor oligosaccharide analogs (H- 2 on LNneoT) in bioengineered bacteria. In this competitive renewal, we focus on the human milk glycans as novel antimicrobials with three major functions - pathogen-binding inhibition, prebiotic activity, and antiinflammatory activity - that protect breastfeeding children against enteric infectious and inflammatory diseases, three projects are proposed pertaining to the human milk glycans: 1) Inhibition of bacterial gastroenteritis; 2) Inhibition of viral gastroenteritis; and 3) Modulation of inflammation, colonization, and mucosal development. In each project, we propose basic, clinical and translational research. Two complementary lines of translational research will be pursued: 1) Developing and testing human milk glycan analogs as novel antimicrobials and 2) testing the secretor phenotype as a novel clinical biomarker for enteric infectious and inflammatory diseases. The projects will be supported by cores in Biometry (Epidemiology, Biostatistics, and Informatics); Glycobiology; and Molecular Biology. Our focus and approach addresses NIH Road Map 2008 priorities pertaining to inflammation, the microbiome, and phenotyping.